Eric Marienthal was born on December 19, 1957, in Sacramento, California, and moved with his family to San Mateo when he was two. He picked up the saxophone in the fourth grade after a teacher discouraged him from the trumpet because of his braces, and his father, an insurance salesman who liked records by Boots Randolph, Nat King Cole and Frank Sinatra, bought him a $400 Selmer. He later added guitar, flute, clarinet and piano. After graduating from high school in Southern California in 1976 he studied at the Berklee College of Music in Boston with the saxophone professor Joe Viola, and he left Berklee with the highest proficiency rating the school gave.

He started working professionally in 1980 with the New Orleans trumpeter Al Hirt. While he was in Hirt's group he auditioned for the Disneyland Band, won the job and left Hirt, then settled in Los Angeles as a staff musician and a studio and live player. Early credits include big-band records with Roger Neumann (1983) and Matt Catingub (1984 and 1985). In 1986 he met Chick Corea, whose records he already admired, and soon afterward joined the Chick Corea Elektric Band. His first record with the group, Light Years (1987), set its long-running lineup with guitarist Frank Gambale, bassist John Patitucci and drummer Dave Weckl, and it won the 1988 Grammy for Best R&B Instrumental Performance. He made six albums with the band: Light Years, Eye of the Beholder (1988), Inside Out (1990), Beneath the Mask (1991), Elektric Band II: Paint the World (1993, on which only Corea and Marienthal remained from the original lineup) and the reunion To the Stars (2004).

During the Elektric Band years he signed with GRP as a leader. His first album, Voices of the Heart (1988), was produced by Corea, who also played on it, and Round Trip (1989) and Crossroads (1990) were produced by Marienthal and Patitucci together. Oasis (1991), made with the producers Jeff Lorber and Russell Ferrante, was his breakthrough and reached the top five of the contemporary jazz chart; Lorber then produced One Touch (1993) and Street Dance (1994), and from Street Dance on his albums also charted on the main jazz list. In the same period he was a regular GRP studio player and a member of the GRP All-Star Big Band, which made three records between 1992 and 1995, including a live album presented by Dave Grusin, and he toured with the bands of Lee Ritenour and David Benoit. Berklee gave him its Distinguished Alumnus Award in 1995.

In 1997 he moved to the i.e. Music label that Ritenour had founded for Verve. Ritenour produced Easy Street (1997), whose title track was a contemporary jazz radio hit, and Harvey Mason produced Walk Tall (1998), a tribute to Cannonball Adderley with Stanley Clarke and Ritenour as guests. Its single "Here in My Heart" spent three weeks at number one on the contemporary jazz chart, and a cover of "Mercy, Mercy, Mercy" reached number five. He also took the lead alto chair in Gordon Goodwin's Big Phat Band, a Los Angeles big band, and he appears on its records from Swingin' for the Fences (2000) through 2023; the band's own website lists him among its reed players as of November 2026. From 2001 to 2007 he made four albums for Peak, the label run by Russ Freeman of the Rippingtons: Turn Up the Heat (2001), Sweet Talk (2003), Got You Covered (2005, a set of covers with Russell Ferrante, bassist Dave Carpenter and drummer Peter Erskine) and Just Around the Corner (2007, produced in part by Brian Culbertson, Lorber and Stephen Lu). Since 1999 he has also led an annual benefit concert for High Hopes, an Orange County program for people with traumatic head injuries, which his official biography says has raised more than $2 million.

From 2010 to 2013 he was a member of the revived Jeff Lorber Fusion, playing on Now Is the Time (2010), Galaxy (2012) and Hacienda (2013). It's Love (2012), produced by guitarist Chuck Loeb, with Lorber, Russell Ferrante, Brian Culbertson and the trumpeter Till Brönner among its guests, came out on the same day as Galaxy. Marienthal and Loeb then made Bridges (2015, Shanachie) with John Patitucci on bass and Byron Landham on drums; it reached number 15 on the jazz albums chart and number six on the contemporary jazz chart. Loeb died in 2017. In 2020 Marienthal recorded Double Dealin' with trumpeter Randy Brecker, with Dave Weckl on drums and John Patitucci on bass; it was nominated for Best Contemporary Instrumental Album at the 64th Grammy Awards. He has also written three instructional books and made instructional videos for Warner Bros. Publications (now Alfred), and since 2015 he has run an online saxophone school with ArtistWorks. His website lists him as music director of the programs produced by Jazz Cruises, LLC.

Marienthal is a contemporary jazz alto saxophonist, and his catalog sits closer to smooth jazz and jazz fusion than to the straight-ahead tradition. AllMusic describes his sound as crystal clear and emotive but cool, a tone that suited smooth jazz radio, and his own records blend jazz-funk, soul, pop and quiet adult contemporary R&B; he has also worked with Elton John, Stevie Wonder, Barbra Streisand and David Lee Roth. His jazz footing comes from the groups he has played in: the Elektric Band's electric fusion, the GRP and Gordon Goodwin big bands, the 1998 Walk Tall tribute to Cannonball Adderley, and a teaching career built on jazz study books. He was already a fan of Chick Corea before he joined that band, and he works with a wide circle of GRP and Peak players, among them Jeff Lorber, Russ Freeman and David Benoit. He plays alto, soprano and flute, with tenor on some albums, and has long used a Selmer Mark VI alto. According to his official biography, Jazziz readers named him one of the year's favorite alto saxophonists alongside David Sanborn and Phil Woods.